JPH0219403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a distance detection device particularly suitable for short-distance position detection using a semiconductor position detection device capable of detecting the incident position of light. .

(Prior Art) A distance detection device using a semiconductor position detection device is known.

FIG. 4 is a schematic diagram for explaining the principle of a distance detecting device using a semiconductor position detecting device.

Light from the light source PD is projected into the front space via the projection lens _L1 .

The reflected light from the object Ob in the front space enters the semiconductor position detection device PSD via the light receiving lens _L2 at a _position separated by a certain base line length D from the light projecting lens L1. The semiconductor position detection device PSD is arranged with its center aligned with the optical axis of the lens _L2 in the base line length direction.

Assuming that the effective length of the semiconductor position detection device PSD is 2l and the point of incidence of light is at a position Δx away from the optical axis of the light receiving lens _L2 , the current flowing out from both terminals is
The following relationship holds between I ₁ and I ₂ .

I ₁ (l - Δx) = I ₂ (l + Δx) Therefore, Δx/l = (I ₁ - I ₂ )/(I ₁ + I ₂ ), and the relationship Δx/p = D/L holds true. Object Ob
The distance to can be calculated from the currents I ₁ and I ₂ .

Japanese Patent Application Laid-Open No. 56-143904 (title of the invention: Optoelectronic Distance Measuring Apparatus) is based on the above principle and proposes a distance measuring apparatus that utilizes a large number of reflective surfaces.

In addition, JP-A No. 60-52710 (name of the invention distance detection device) does not use a semiconductor position detection device that can detect the incident position of light, but it similarly detects distance based on the principle of triangulation. In order to make the device more compact, we have proposed using the inner surface of the cylinder as a reflective surface.

This device is planned to be used as a moiré topography device. The apparatus is configured to project an image from a light source through one lens and the reflective surface, and to receive and evaluate the reflected light through the reflective surface and the lens.

(Problems to be Solved by the Invention) The inventors of the present invention utilized the principle of the distance detection device described above and studied the problems when distance detection is performed using a semiconductor position detection device.

FIG. 5 is a schematic diagram of a distance detection device created by the inventor of the present invention in order to study the problems.

Light from the light source 4 is projected onto the object to be measured 6 in front via the lens 2.

The reflected light from the object to be measured 6 located at position a is reflected by the inner surface of the cylindrical mirror 1, is again focused by the lens 2, and is made incident on the semiconductor position detection devices 3 and 5.

Note that, in principle, measurement is possible using only one of the semiconductor position detection devices.

When the object to be measured moves by ΔZ to position b shown by the two-dot chain line, the light ray follows the optical path shown by the two-dot chain line,
On the semiconductor position detection devices 3 and 5, Δx
The light is focused at a position moved away from the optical axis by .

By calculating the output current of the semiconductor position detection device 3 as described above, the distance to the object to be measured 6 can be detected.

By increasing the focal length of the light-receiving lens 2 and moving the semiconductor position detection device 3 from the position (B) to the position (B') shown by the dotted line, the distance measurement resolution can be increased.

By arranging the semiconductor position detection device 3 at position B', the amount of movement of the focusing position on the semiconductor position detection device 3 relative to the amount of movement (ΔZ) of the object to be measured 6 is expanded from Δx to Δx'. . The following relationship (1) holds between them.

Δx'=(B'/B)Δx...(1) FIG. 6 is a schematic diagram showing the optical path formed by the distance detecting device.

The sum total (I ₀ ) of light that does not contribute to distance measurement and signal light that enters the semiconductor position detection devices 3 and 5 is given by the following equation.

I ₀ = In ₀ + Is + In ₁ + Ine ... (2) In ₀ : The light beam from the light source 4 is reflected on the front and back surfaces of the lens 2 and goes around Is: The reflected light from the object to be measured 6 is reflected from the cylindrical mirror 1. Signal light reflected from the inner surface and condensed by lens 2 (not shown) In ₁ : Of the reflected light from the object to be measured, light that is not reflected by cylindrical mirror 1 and directly enters lens 2 and wraps around In: Part of extraneous light other than light source 4 Of the above _I0 , only Is has distance information; other lights become harmful components when distance calculations are performed in the connected circuit system, and are not included in distance measurement. This becomes a factor that causes errors.

Of these, most of the external light (Ine) in a wavelength range other than the emission wavelength of the light source can be removed by an optical band filter. Further, the light source can be turned on in pulses, and the light transmitted through the optical band filter can be photoelectrically converted by the semiconductor position detection devices 3 and 5, and then removed by synchronous detection.

On the other hand, In ₀ and In ₁ are difficult to remove using an electrical arithmetic circuit system, so it is possible to reduce internal reflection by coating lens 2 with an anti-reflection film or by applying absorbing paint to the inside of the optical system. There is a way to do this, but the effect is small.

Further, it is not easy to make the inner surface of the cylindrical mirror a mirror surface, and this may cause an increase in manufacturing costs.

As described above with respect to this device, if the focal length of the lens 2 is increased, the distance measurement resolution can be improved, but there is a problem in that the shape becomes larger and the effect of miniaturization by the cylindrical mirror is lost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a distance detection device that can solve the problems described above and is suitable for miniaturization.

(Means for Solving the Problem) In order to achieve the above object, a distance detection device according to the present invention projects light from a light source into a space ahead through a projection lens, and uses reflected light from the front to reflect light from the projection lens. A light-receiving element that can detect the incident position via the light-receiving lens receives light at a position a certain baseline length away from the light lens, and its output is processed by an arithmetic circuit to obtain information on the distance to the reflective object in the space in front of it. In the distance detection device, an optical element having a refractive power for refracting light from the reflecting object in the direction of the optical axis of the projecting lens is arranged in front of the light receiving lens.

(Example) Hereinafter, the present invention will be described in more detail with reference to the drawings and the like.

FIG. 1 is a diagram mainly showing the optical path with an embodiment of the optical system of the distance detecting device according to the present invention.

The light projecting lens 12 is arranged so that its optical axis is aligned with that of the lens 7.

Lens 7 is formed by removing the center portion of a convex lens.

The light from the light source 13 is focused by the projection lens 12 and illuminates the object to be measured 6 in front through the removed portion of the center of the lens 7 .

The reflected light from the object to be measured 6 is refracted by the lens 7 in a direction that reduces the angle with the optical axis direction of the light projecting lens, and is made incident on the light receiving lenses 8 and 9.

The light focused by each light receiving lens 8 and 9 is projected onto the light receiving surface of semiconductor position detecting devices 10 and 11, respectively.

In this optical system, the distance Z to the position indicated by the broken line in FIG. 1 is given by the following equation using the optical paraxial ray region calculation method.

Z = (bf ₂ - eΔx) f ₁ / (bf _{2 -} eΔx + f ₁ Δx) ... (3) where f ₁ : Focal length of objective lens 7 f ₂ : Focal length of light receiving lenses 8 and 9 e: Objective lens and the light receiving lenses 8 and 9: distance b from the electrical center position of the semiconductor position detection devices 10 and 11 to the center of gravity of the focused spot light: optical axis of the objective lens 7 and the light emitting lens 12 and the optical axis of the light-receiving lenses 8 and 9 (corresponding to the base line length of the triangulation method) Z: distance from the objective lens 7 to the object to be measured 6 In equation (3), when Δx = 0, the object to be measured 6 The distance to (Z ₀ ) is equal to f ₁ .

Here, in order to increase the distance resolution, it is sufficient to increase the ratio of the amount of movement of the spot light (Δx) to the amount of change in Z (ΔZ). ΔZ can be found from equation (4).

ΔZ=Z ₀ −Z ₁ =f ₁ ² Δx/(bf ₂ −eΔx+f ₁ Δx) ...(4) When f ₂ ≫Δx in equation (4), ΔZ becomes equation (5).

ΔZ=f ₁ ² Δx/bf ₂ ...(5) From equation (5), the ratio of Δ× of the amount of change ΔZ is expressed as equation (6).

Δx/ΔZ=bf ₂ /f ₁ ² ...(6) As is clear from equation (6), when the focal length f ₁ and baseline length b of the objective lens 7 are constant, the distance resolution is The height increases approximately in proportion to the focal length _f2 .

In FIG. 1, even if f ₂ becomes longer, the size in the base line length direction remains constant, and it is only necessary to change the length in the Z direction.

FIG. 2 shows the distance Z calculated by calculating the position of the light spot formed on the semiconductor position detection device by the optical system.
FIG. 2 is a block diagram showing an embodiment of an arithmetic circuit for calculating .

As the light source 7, an infrared light emitting diode (for example, L1909 type manufactured by Hamamatsu Photonics Co., Ltd.) is used.
The drive circuit 14 is a drive circuit for causing the light source 7 to emit pulsed light.

As the semiconductor position detection devices 10 and 11,
PSD, for example S2153 from Hamamatsu Photonics Co., Ltd.
Use a mold.

The respective semiconductor position detection devices 10 and 11 have the same shape and sensitivity, and are arranged symmetrically on the optical axis of the lens 7.

Assuming that the amount of light incident on each semiconductor position detecting device 10, 11 is equal and that the incident position is symmetrical, the current extracted from the electrode from the light source 13 of each semiconductor position detecting device 10, 11 is i ₁ , and the current from the outside is Let i ₂ be the current extracted from each electrode. The outer electrode and inner electrode of each semiconductor position detection device 10, 11 are connected in common.

The purpose of this connection is to double the output current and improve detection sensitivity.

The current 2i ₁ +in extracted from the inner electrode (where in is an external photocurrent) and the current 2i ₂ +in extracted from the outer electrode are converted into signal currents 2i 1 and 2i 1 +in by signal current extraction circuits 15 and ₁₆ , respectively. After only 2i ₂ is extracted and amplified, the logarithmic conversion circuit 17
and 18, and the differential amplifier 19 performs the calculation of logi ₂ -logi ₁ =logi ₂ /i ₁ .

This calculated value is held by the sample and hold circuit 20, and data corresponding to the distance Z can be obtained based on this.

FIG. 3A shows a half optical system of the optical system shown in FIG.

As described above, the purpose of providing a target optical system and a pair of semiconductor position detection devices is to improve detection sensitivity. Therefore, when sufficient reflected light is obtained, a similar distance detection becomes possible by associating the light source and the semiconductor position detection device with the optical system shown in FIG. 3A.

As shown in FIG. 3B, a similar effect can be obtained by replacing the lens 7 with a prism 30.

(Effects of the Invention) As described above in detail, the distance detection device according to the present invention projects light from a light source into a space in front of the light source through a light projecting lens, and directs reflected light from the front from the light projecting lens to a certain base line. In a distance detection device that receives light with a light-receiving element that can detect the incident position through a light-receiving lens at a long distance, and processes the output with an arithmetic circuit to obtain information on the distance to a reflective object in the space in front of it, An optical element having a refractive power for refracting light from the reflecting object in the direction of the optical axis of the projecting lens is disposed in front of the light receiving lens.

Therefore, the light from the light projection lens is not affected by the optical element, so that noise related to light projection can be significantly reduced.

Furthermore, if a pair of the optical elements is provided and a device for detecting the incident position of light is provided, detection sensitivity can be improved.

[Brief explanation of drawings]

FIG. 1 is a diagram mainly showing an embodiment of the optical system and its optical path of the distance detecting device according to the present invention. Second
The figure is a block diagram mainly showing an embodiment of the arithmetic circuit of the distance detecting device according to the present invention. FIG. 3 is an optical path diagram showing another embodiment of the optical system, and FIG.
Figure B shows an example in which an optical element with refractive power is realized using a lens part, and Figure B shows an example in which it is realized using a prism. FIG. 4 is a schematic diagram for explaining the principle of a distance detecting device using a semiconductor position detecting device. FIG. 5 is a schematic diagram of a distance detection device created by the inventor of the present invention in order to study the problems. FIG. 6 is a schematic diagram showing the optical path formed in the distance detecting device. 6...Object to be measured, 7...Lens, 8, 9...Light receiving lens, 10, 11...Semiconductor position detection device,
12...Light projection lens, 13...Light source, 14...Light source drive circuit, 15, 16...Signal current sampling circuit,
17, 18...logarithmic conversion circuit, 19...operational amplifier, 20...sample hold circuit, 30...prism.

Claims (1)

[Scope of Claims] 1. Light from a light source is projected into the front space through a light projecting lens, and the reflected light from the front is transmitted through a light receiving lens at a position a certain baseline length away from the light projecting lens to determine the incident position. In a distance detection device that receives light with a light-receiving element that can detect light and processes the output with an arithmetic circuit to obtain information on the distance to a reflective object in the space in front of it, the light from the reflective object is transmitted in front of the light-receiving lens. A distance detection device characterized in that it is configured by arranging an optical element having a refractive power for refraction in the optical axis direction of the light projecting lens. 2. Claim 1, wherein the optical element is a positive lens that is provided in front of the light projecting lens so that its optical axis is aligned with the light projecting lens, and the front of the light projecting lens is penetrated. Distance detection device as described. 3. The detection range and accuracy of the distance detection device are determined by the focal length of a positive lens through which the front of the light emitting lens is penetrated, the focal length of the light receiving lens, and the base line length. Distance detection device. 4. The distance detection device according to claim 1, wherein the optical element is a prism that refracts the reflected light in a direction approaching parallel to the optical axis of the projection light. 5. The distance detection device according to claim 1, wherein the light receiving element is a semiconductor position detection device. 6 A light receiving device that can project light from a light source into the front space through a light projecting lens, and detect the incident position of the reflected light from the front through a light receiving lens at a position a certain baseline length away from the light projecting lens. In a distance detection device that receives light with an element and processes its output with an arithmetic circuit to obtain information on the distance to a reflective object in a space in front of the device, a pair of the light receiving lenses are provided at positions symmetrical to the optical axis of the light projecting lens, A pair of optical elements having a refracting power to refract the light from the reflecting object in the optical axis direction of the light projecting lens is disposed in front of each of the light receiving lenses, and the light receiving elements are respectively arranged with respect to the light receiving lenses. . A distance detection device, wherein the outputs of the light receiving elements are processed by the arithmetic circuit so that the outputs are added.